# Surface tension in food

Based on a related question, some of us are curious about surface tension in liquids commonly used in food and drink. There's a table on Wikipedia containing a tantalizing amount of information, including:

• The surface tension of water decreases from 76 mN/m to 59 mN/m as temperature increases from 0C to 100C. It's 72 mN/m at warm room temperature, 25C.

• 10% acetic acid (very strong vinegar) has a substantially reduced surface tension (55 mN/m at 30C)

• Alcohol can strongly reduce surface tension, to 46 mN/m at 11% and 30 mN/m at 40%.

• A concentrated sucrose syrup (55%) has somewhat higher surface tension than water, 76 mN/m at 20C.

• Very salty water (6M, compared to seawater at .6M) has higher surface tension, 83 mN/m at 20C.

Of interest would be:

• How does surface tension typically depend on temperature? (Does it always decrease with increasing temperature?)

• How do various everyday solutes (e.g. sugar) and mixture components (e.g. alcohol, acetic acid) affect surface tension of water? Actual data on measured surface tension of liquids would be wonderful - for example, what is the surface tension of milk, tea, vinegar, syrup, various alcoholic beverages, or anything else we commonly cook with or drink? What determines whether something increases or decreases the surface tension of water?

• Are there any more exotic (but edible!) solutes or mixture components with dramatic effects on surface tension? Especially interesting would be ones without flavor, which could be used to tweak existing liquids.

Note: I posted a related question on the physics stackexchange.

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+1 for the nice question. For dramatic effects, try applying pressure to a starch slurry (for a slightly wide definition of edible). – rumtscho Sep 9 '11 at 20:19
I think this question is fairly irrelevant in the realm of cooking. Textural perceptions of a given liquid are going to be dominated it's viscosity. – Nick T Nov 7 '11 at 20:01
@NickT: Sure, if you're drinking it - though still, I think that we notice things that seem slippery. But what if you want to turn it into a foam? What if you don't want it to foam? People do crazy things these days, and surface tension affects some of them. – Jefromi Nov 7 '11 at 22:06
@Jefromi 'slippery' would be a function of interface properties, not just one thing in isolation – Nick T Nov 7 '11 at 22:08
@NickT: Sorry for the imprecision there. I'm aware that material properties are a complex thing. My point was that there were situations in which it could have a noticeable effect. – Jefromi Nov 7 '11 at 22:48